This
white paper was originally developed in Fall 2010 as part of a report to the
Dean of Engineering at the University of Maryland from a committee assessing
opportunities in Global Sustainability.Since then, many students have approached me about defining
sustainment.Most come with the preconceived notion that “sustainment” and
“sustainability” only refer to environmental sustainability, which is
unfortunate.Sustainment and sustainability are concepts that are much older and
broader than just the environmental context that the popular media relates
them to.The objective of this white paper is to articulate a common
definition of sustainability and/or sustainment that can be used as a basis
for orienting, defining and integrating various diverse efforts ranging from
business to technology and environment.

There
is a difference between the implied meanings of the words sustainability and
sustainment, but first, let’s consider the root.The root for both words is “sustain”. “Sustain”
comes from the Latin sustenare
meaning “to hold up” or to support, which has evolved to mean keeping
something going or extending its duration (reference 1). The most common
non-specialized synonym for sustain is “maintain”. Although
maintain and sustain are sometimes used interchangeably, maintenance usually
refers to activities targeted at correcting problems or fixing defects, and
sustainment is a more general term referring to the management of system
evolution (reference 2).Sustainability
can also mean static equilibrium (the absence of change) or dynamic equilibrium
(constant, predictable or manageable change) (reference 3).

Today,
sustainability (or more accurately sustainable development) is most widely
identified with environmental sustainability - the ability of an ecosystem to
maintain ecological processes and functions, biological diversity, and
productivity over time (reference 4).Alternatively,
“sustainment” has come to be associated with the process of assessing and
improving a system’s ability to preserve its function and value under
continued operation, maintenance and unexpected change.[1]The concept of sustainability appears throughout nearly all disciplines,
most notably in the contexts of business, technology and environment.

The
most widely circulated definition of sustainability is attributed to the
Brundtland Report
(reference 5), which is often
paraphrased as “development that meets the needs of present generations
without compromising the ability of future generations to meet their own
needs.” This definition was created in the context of environmental
sustainability, however, it is useful and applicable for defining all types of
sustainability.[2]

Unfortunately,
the definition of sustainability has been customized by many organizations to
serve as a means to an end, and in some cases it has been abused to serve
special interests and marketing,[3]
and defining sustainability has become a cottage industry for people who are
seeking grants (reference 7).

Environmental
sustainability definitions abound.We
desire a more general definition that can apply to environmental sustainability,
but is also applicable to sustainment in the business and technology sense.While it is easy to agree on a definition of “unsustainability” (not
able to continue), the definition of sustainability is more elusive.Here are three proposed definitions:

1)The capacity of a system to endure.

“system” – this could refer to an actual physical item,
e.g., a product, which could be a laptop computer, an airplane or infrastructure
(the electronic power grid).The
system could also refer to a service or an institution, e.g., the U.S. Social
Security Administration or the
University
of
Maryland
.It could refer to a system that a
product (or group of products, or users of the products) resides in, e.g., an
eco-system.Lastly, it could be a
process, e.g., a manufacturing process.

“endure” – this is a relative term that really means to
endure from the viewpoint of the system’s stakeholders.If the system is an eco-system, then the stakeholders are the population
of people who reside in or otherwise care about the eco-system.If the system is a specific product, than the stakeholders are the
customers and the organization that has to support the product.

2)Development, production, operation and management of systems that
maximize the availability of goods and services while minimizing their
footprint.

“availability” – this represents the
fraction of time (or some other measure of life) that a good or service is in
the right state, supported by the right resources, and in the right place when
the customer requires it (the “customer” could be an individual, a company,
a city, a geographic region, etc.).

One
spin-off from the definitions above is a focus on “sustainment-dominated”
systems, (reference 8).A
sustainment dominated system could be defined as a system for which the lifetime
footprint significantly exceeds the footprint associated with making it.Where (as defined above), footprint refers to any kind of impact one is
interested in (or is relevant to the specific stakeholders), e.g.,
environmental, cost (economics), human health, energy required, and/or other
resource consumption (water, materials, labor, expertise, etc.).

Defining
sustainment-dominated systems provides the opportunity to make a distinction
between high-volume, low cost consumer products and larger, higher-cost systems
such as airplanes, infrastructure, and institutions.

Two
related areas have recently appeared that are worth mentioning in the context of
sustainability.

The
first is “performability engineering”. The term performability was
introduced in 1980 by John Meyer (reference 9) in the context of evaluation of
highly reliable aircraft control computers for use by NASA to collect attributes
like reliability, maintainability and availability.Performability engineering widens the definition of performability to
also include sustainability in order to reflect a holistic view of designing,
producing, and using systems or services that will satisfy the performance
requirements of a customer (reference 10).

Viability
has been defined as a monetary and non-monetary quantification of
application-specific risks and benefits in a design/support environment that is
highly uncertain, (reference 11).Traditional
“value” metrics go part of the way toward defining viability by providing a
coupled view of performance, reliability and acquisition cost, but they are
generally ignorant of how product sustainment is impacted. The concept of
viability was developed in the context of technology insertion (redesigning
systems or products) and attempts to couple sustainment with more conventional
value metrics.Viability assessments
usually include hardware, software, information and intellectual property
aspects of the product or system and goes beyond just an assessment of the
immediate or near-term impacts of a design, in that it evaluates the candidate
design (or candidate architecture) over its entire lifetime.

[1]
Interestingly, even though sustainability and sustainment are very closely
related in a semantic sense, they are rarely interchanged in environmental
sustainability practice, e.g., environmental sustainability organizations
never refer to what they are doing as sustainment or sustainment
engineering, however organizations that maintain systems (sustainment
organizations) will often also use the word sustainability to describe what
they do.

[2]
For example, for technology sustainment, “present and future
generations” in the Brundtland definition can be interpreted as the users
and maintainers of a system.

[3]
Wild Planet Sardines are apparently “sustainability caught” off the
coast of
California
and then shipped to a cannery in
Vietnam
and finally returned to grocery store shelves in
California
(reference 6).